1. Field of the Invention
The present invention relates to novel catalysts and to the utilization thereof in the oxidation of hydrogen sulfide and/or organosulfur compounds to sulfur dioxide.
2. Description of the Prior Art
Certain industrial effluents, and in particular the effluents originating from Claus reaction units, contain sulfur and/or polluting sulfur compounds which can be oxidized, and these gases must be treated such as to effect conversion of said sulfur/organosulfur compounds to sulfur dioxide by oxidation. The sulfur compounds which are present, in particular, in these effluents are principally hydrogen sulfide and organic sulfur compounds such as carbon disulfide and/or carbon oxysulfide and/or mercaptans.
It is known to this art to treat effluents containing hydrogen sulfide by burning them at high temperatures, but this method is now obsolete, both because of the high energy consumption entailed and, from a technical point of view, because of the considerable amount of oxygen which is required therefor.
Furthermore, catalytic processes for treating gases containing hydrogen sulfide too have already been proposed to this art; however, these processes have the disadvantages of being insufficiently catalytically active, of not effecting a complete oxidation of the hydrogen sulfide at a sufficiently low temperature, and of having an inadequate catalyst life.
Thus, it has to date been proposed, according to U.S. Pat. No. 1,900,751, to oxidize hydrogen sulfide to sulfur dioxide in the presence of a catalyst comprising active elements deposited on a support of silica gel or of calcined clay, the active phase elements being selected from among the following metals: nickel, iron, cobalt, manganese, zinc, copper and, if appropriate, chromium, vanadium, molybdenum, cerium, uranium, thorium, tungsten, silicon and carbon, and comprising up to 10% of compounds of lead, bismuth, alkali metals and alkaline earth metals, it being possible for these compounds to be oxides, hydroxides, carbonates and sulfates. It should be noted that, according to page 5, lines 94 and 96, of the said patent, the catalysts thus proposed are so unsatisfactory that it is necessary to increase the reaction temperature by 5% every 3 days.
A process for the oxidation of hydrogen sulfide to sulfur in the presence of a catalyst comprising the sulfates of the following metals: cadmium, cobalt, copper, iron, lead, nickel, tin, silver and zinc, deposited on a support of active alumina or of clay, is featured in British patent specification No. 769,996.
And a process for the oxidation of hydrogen sulfide to sulfur dioxide in the presence of a substantial proportion of hydrogen, such as to avoid the formation of SO.sub.3, and in the presence of a catalyst comprising vanadium oxide deposited on a support of a non-alkaline, porous refractory oxide, has also been proposed; compare U.S. Pat. No. 4,092,404.
It has also been demonstrated that organic sulfur compounds are as polluting in nature and are as noxious as is hydrogen sulfide. Thus, serious need exists in this art for improved catalysts which enable removal of hydrogen sulfide and/or organic sulfur compounds in the form of sulfur dioxide.